As is known, tumours are one of the main causes of death in the world. In particular, pulmonary tumours are the highest in terms of incidence, as they represent about 12% of all the new cases of cancer, and constitute the main cause of death by cancer in the world, in both men and women.
In Europe about 400,000 new cases are diagnosed per year (80% men, 20% women). In Italy the epidemiology of pulmonary cancer is similar, with an incidence of 34,000 cases per year of which 7,000 are women and 27,000 men.
Sadly the incidence and the mortality are very similar due to the highly lethal nature of pulmonary tumour: world-wide mortality 27,500, of which 22,000 mend and 5,500 women. This epidemiological data and the scarce level of treatability of the illness underline the importance of identifying methods which are able to identify as soon as possible any subjects who might be at risk of developing pulmonary cancer. Further, it is of great interest to develop procedures which can help in the correct diagnosis of tumours, in particular pulmonary tumours present in an individual subject under examination.
Notwithstanding these needs, tumour markers available today are for diagnostic use, i.e. they identify the patients when the disease has already developed such as to be identifiable with imaging methods (spiral CT scan). These markers are however few and not specific and essentially comprise biochemical markers such as the evaluation of the protein CEA (Carcinoembryonic Antigene) and some cytokeratins such as TPA, TPS and Cyfra 21.1.
Also known is a proteomic test (5-protein profile) on the serum, at present proposed by Vermillion Inc. and used to indicate a probability (score from 1 to 10) that ovarian masses might be of a malignant nature. This test is used for women who already present ovarian masses of a non-defined nature.
With specific reference to pulmonary tumours, although in recent years important improvements have been made in the treatment of oncological patients, there is however a need to develop more effective methods which can lead to a faster therapeutic intervention in clinical management of many types of tumours.
At present the majority of pulmonary tumours are diagnosed at a late stage, when the symptoms are clinically evident and, for example with reference to Non-small-cell lung carcinoma (NSCLC), only a third of patients with NSCLC exhibits a surgically-resectable disease, an approach which remains the most effective treatment for this type of tumour.
Notwithstanding recent progress in treatment of pulmonary cancer after resection and the use of specific treatments for determined molecular targets, the rate of healing of non-small-cell lung carcinoma (NSCLC) remains low due to the reappearance thereof in patients that are resistant to drugs or who present metastasis.
The effectiveness of the spiral CT scan in identification of pulmonary cancer in heavy smokers is under evaluation in various randomized clinical studies in Europe and the United States. Owing to the its high level of sensitivity there remain various critical points for its use in modern clinical practice, such as over-diagnosis of indolent nodules, with a consequently high frequency of non-necessary treatments and the verification of the effective impact on mortality.
In this context, in recent years microRNAs have been identified (herein below also MiRNA) as a new class of circulating bio-markers which by their nature seem to be very stable and highly specific tissue (Chen X, Cell Res, 2008). MiRNAs are small non-coding RNA molecules (length 19-25 nucleotides) having a regulatory function which are able to modulate the expression of several target genes involved in various molecular mechanisms, among which those involved in transformation processes.
The development of high-throughput technologies has enabled the study of overall expression of the profiles of miRNA in cancer (microRNAome) (Cummins J M et al., Proc Natl Acad Sci USA, 2006), revealing that there exist hundreds of miRNA whose expression is deregulated in tumours (Croce C M, Visone R, AJP, 2009; WO2009/070653, The Ohio State University Research Foundation).
Apart from the tissue specificity, miRNA possess a high degree of stability, ease of detection and association with known clinical-pathological parameters (Lu Jet al., Nature, 2005).
Tests have also been carried out to determine whether miRNAs are stable, detectable and quantifiable not only in the tissues (both deep-frozen and fixed in formalin or paraffin) but also in the bodily fluids. The results of this research have demonstrated that miRNAs are also present in the blood circulation (whole blood, serum and plasma), where they are found in stable form protected by endogenous RNAsi. Circulating miRNAs are detectable and quantifiable and the studies which have taken their levels in oncological patients' biological fluids under examination have reported that some of them present deregulated levels with respect to healthy individuals (Heneghan H M et al., Ann Surg, 2010; Mitchell P S et al., Proc Natl Acad Sci USA, 2008; Chen X, Cell Res, 2008).
Recent publications report the profile of miRNAs circulating in the serum and plasma of patients having pulmonary tumour (Hu Z, Clin Oncol, 2010; Silva J, Eur Respir J, 2010 Shen J, Lab Invest, 2010).
Notwithstanding the presence of diagnostic imaging systems and the studies relating to microRNAs, there is still the need to identify procedures which are able to identify, with a certain degree of anticipation, individuals at risk of developing pulmonary cancer and possibly able to predict the development of the forms of cancer, in particular pulmonary tumour, that are more aggressive and lethal. There is also a need to improve the degree of reliability of diagnostic techniques at present available.